A conventional vehicle-mounted GPS (global positioning system) unit can provide high-precision positioning, but may require time to obtain satellite information for successful positioning. The cold boot process of the vehicle-mounted GPS unit can take up to 30-40 seconds or longer for successful positioning in remote areas. However, the startup time of a vehicle-mounted operating system is generally within 10 seconds, which is far shorter than the boot-up time of the vehicle-mounted GPS unit. Thus, no positioning information would be available for the vehicle-mounted operating system while waiting for the vehicle-mounted GPS unit to activate. Hence, accelerating the GPS positioning speed of the vehicle-mounted navigation system is a key technical problem to be addressed in the current automotive field. Therefore, there is a need for a quick positioning method and an associated vehicle-mounted system to address the above technical problem.